I didn't expect so many problems with this module, to be honest. There is many tutorials but none of them doesn't explain some less known thingk. One of them is how to use ZS-040 module with EN pin instead of KEY.
Trying to understand how to use it I have found this site as the best source in internet. Unfortunately, many things there were explained on the best possible way.
I hope that a lot of people from this forum is able say many things about using of this module. Thing which I would like to hear is explanation of these 4 ways of entering to AT mode. Also, I would like to hear, is it possible to use HC-05 without dividing resistors on RXD and TXD pins on Arduino Uno?
All HC-O5s are the same. The differences are in the breakout boards, of which there are two types - those with a button for configuration, ZS-040 etc., and those without, JY-MCU. The EN pin and the KEY pin serve the same purpose.
You don't need to configure the HC-05 in order to use it, and the first thing to consider is if you really need to do so. Most users don't but , if you do, the Martyn Currey site is the best resource.
It is possible to use the HC-05 without the voltage divider, I did so for years, but nobody will tell you is is a good idea.
You might find the following background notes useful
Thank you too, Nick. I've already seen that PDF file a few days ago. To be more precise, I want to know how to enable AT mode connecting 3,3V on pin 34? Why creators of these module didn't allow us to do that much easily than now? Why we have to press small button during powering on if it is not so easy to do in many cases? Couldn't they enable to do that during module is turned on?
Gosh:
I want to know how to enable AT mode connecting 3,3V on pin 34? Why creators of these module didn't allow us to do that much easily than now?
Well, they do. pin 34 of the HC-05 is connected to the KEY pin on a breakout board. I can only assume you are using a bare module, in which case you deserve all the grief you are getting, but the situation can be relieved by investing $1-20 in a blank breakout board on eBay.
Why we have to press small button during powering on if it is not so easy to do in many cases? Couldn't they enable to do that during module is turned on?
Ah, yes. That is interesting, and you don't have to. The older JY-MCU board does not have a button. This may normally be seen as a disadvantage, but it is not necessarily the case. I understand using a button makes the job easier, but not having a button means you can configure Bluetooth automatically, i.e. no human intervention.
The HC-06 and HM-10 are in AT mode as soon as power is turned on, and stay that way until a connection is made.
Do I have to connect TX and RX pins to Arduino for AT mode or not? By logic, I don't need to because Arduino has to do nothing with AT mode of a Bluetooth controller. At this moment I just want to insert into AT mode without additional sketches but I can't. Devices have been paired fine but if I press small button during powering on I cannot pair with the module anymore. What I am doing wrong?
Arduino has everything to do with AT mode - unless you come up with something else to send the AT commands, which is indeed possible but rather pointless, and best left to others..
Assuming you already have an Arduino, the obvious way to use AT mode is by means of an Arduino programme. Check the Martyn Currey website, he is the guru on ZS-040.
Bluetooth has two mutually exclusive modes, AT mode, and communications mode. It would appear that you are succeeding with both; just don't try to use both at the same time.
The reason why I asked about that is that I tried to send some AT commands via PC's Bluetooth port and mobile phone. As I told, Hc05/ZS040 doesn't accept these commands. My last guess was that it could be related with lacking of TX/RX connection with Arduino because I don't see any other reason for that.
Martyn Currey website is fine but I couldn't find answer on my question there. I've tried with pushing of button during powering on, didn't help. LED blinks slowly but module doesn't accept commands.What else I can do?
Gosh:
The reason why I asked about that is that I tried to send some AT commands via PC's Bluetooth port and mobile phone. As I told, Hc05/ZS040 doesn't accept these commands. My last guess was that it could be related with lacking of TX/RX connection with Arduino because I don't see any other reason for that.
Read reply #7 again. You cannot send AT commands by bluetooth, only by serial.
I've tried with pushing of button during powering on, didn't help. LED blinks slowly but module doesn't accept commands.
It clearly did help, and quite a lot. You push the button to get into AT mode. The slow flash indicates that you are in AT mode. Therefore it did help.
If I may to ask, why we than have phone apps for communicating with HC-05 if we cannot go directly to AT mode without using of Arduino itself? I still can't believe that a smart module cannot establish connection independently.
And which Read Martyn Currey post to read again? There's a lot of them (although I've read many of them)
There is no phone app for configuring bluetooth, for obvious reasons. And "a smart module cannot establish connection independently" simply because there is nothing to connect to That is just the way it is with bluetooth. I'm sure it is possible to use a phone to reconfigure bluetooth via Arduino by the simple expedient of sending a signal to trigger to a pre-programmed sequence of AT commands, but I don't know if anybody has bothered, as there are probably better non-bluetooth ways to achieve the same end.
If you have a bluetooth module with a button, the section you need to read is that which specifically addresses the modules with a button. I have only ever needed to configure an HC-05 once, and even that was later to be found unnecessary, and I used Currey's notes that specifically addressed the zs-040 board. It wasn't hard, and worked first time.
I have had some kudos by running notes on bluetooth but I only fleetingly talk about configuration, and simply link to the Martyn Currey website. He is the guru, and I believe he has the best presented notes on this.